Method of forming rigid contact tails



Aug. 4, 1964 R; TRAVIS I 3,142,891

METHOD OF FORMING RIGID CONTACT TAILS Filed April 18. 1961 I4 k INVENTOR.

LAWRENCE ROBERT TRAVIS 45 J I ATTORNEYS United States Patent O 3,142,891 METHOD OF FORMING RIGID CONTACT TAILS Lawrence R. Travis, Melrose Park, Pa., assignor to Elco Corporation, Philadelphia, Pa., a corporation of Pennsylvania Filed Apr. 18, 1961, Ser. No. 103,745 2 Claims. (Cl. 29155.55)

This invention relates to a method of forming rigid contact tails and, more particularly, it relates to a method of stamping out contacts from a strip of relatively thin material and then modifying the dimensions of the tail section of the contact in order that it may be stiffened to improve its utility. One suggested use for contacts modified by the process of this invention is in connection with automatic wire wrapping machines which wrap a free lead from an outside circuit about the contact tail. The pressure of winding should be great enough that the lead wire becomes embedded in the contact tail to cold weld the wire to the tail. Thus, the tail should be stiff enough to withstand wrapping pressures.

In the manufacture of electrical contacts to be assembled in connector members or otherwise, a web of metallic material is subjected to the action of a progressive die which in predetermined sequence, stamps, cuts, forms or otherwise converts the contact from an undefined area of material to a desired contact form. However, this type of contact may not be completely satisfactory in itself.

Generally, a contact consists of a head section and a tail section. The head section is adapted, in the case of a female contact and also in many hermaphroditic contacts to clamp upon or grasp a mating contact. Such clamping or grasping action is usually of a resilient nature. Thus, it is desirable to employ a relatively thin web of metallic material as a bent or formed thin material is more resilient than a bent or formed thicker material. However, the contact tail should be relatively thick so that it will be stifi. A stiff tail is desirable because it will withstand the pressures of an automatic wrapping machine. A preferred stifi tail is one that is of square cross-section. Such a tail renders the contact more easily handled. Moreover, a square tail can be wrapped with a constant wrapping tension as compared with a rectangular tail wherein the wrapping about a longer side will be accomplished with a tension different from the wrapping of a shorter side. Additionally, a wrapped square tail will not tend to become warped or twisted, whereas a wrapped rectangular tail is unbalanced in the sense that the moment produced by the interaction of the tension of the wrapped wire and the long side of a tail can overbalance the moment of the wrapped wire and a short side of the tail.

However, the contact for economy purposes should be of a one-piece construction and yet should have contradictory properties, namely, a resilient head section of thin material which will possess the requisite resiliency, and a tail portion of thicker material and preferably square dimensions to possess the requisite stiffness.

Prior efforts to solve'this' problem have resulted in a rectangular tail which is generally unsuitable for automatic wrapping machines requiring a square tail. The use of thicker material is, of course, unsatisfactory because resiliency in the head section is sacrificed. Other prior efforts included providing a tail which has been bent to a V-shaped construction or doubled upon itself. Neither of the-foregoing techniques produced a square tail. Moreover, the technique of doubling the tail on itself was difiicult to accomplish in practice and there was an undesirable sliding action between the doubled halves. In addition, there was a tendency for salts from plating solutions to crystalize between the doubled halves.

It is accordingly an object of the present invention to provide a one-piece electrical contact having contradictory properties.

3,142,891 Patented Aug. 4., 1964 A further object of this invention is to provide a onepiece electrical contact which is relatively thin and resilient at its head portion and relatively thick, rigid and of square cross-section at its tail portion.

Yet a further object of the present invention is to provide a one-piece electrical contact having different cross sectional areas at its head and tail portions and yet being simply and economically manufactured.

Still another object of the present invention is to provide a one-piece electrical contact which possesses corners sharper than those produced by a cutting action whereby the leads of an outside circuit wrapped about the contact will be embedded more deeply into the contact tail thereby achieving a stronger cold weld.

The foregoing as well as other objects of the invention are achieved by employing a progressive die or equivalent apparatus to produce a contact from a relatively thin sheet of material, subjecting the tail portion to the action of coining dies which exert a cam action on the tail section so that the metal of the tail section is caused to flow (cold working) thereby to convert the tail section from a generally thin rectangular shape to a square shape or some other shape having a thicker dimension than previously. Such cold working is produced, for instance, by the side camming action of coining dies or by the action of an overhead press brought to bear on the smaller opposing sides of the tail section to convert it to a generally square shape or some other shape of thickened dimensions.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of a contact manufactured in accordance with the present invention;

FIG. 2 is an enlarged sectional view taken along the lines 22 of FIG. 1 and showing a male probe making electrical and mechanical contact with the resilient fingers of the head section of the contact;

FIG. 3 is a sectional view similar to FIG. 2' but showing a rectangular probe member received between the resilient fingers of the head portion of the contact;

FIG. 4 is a perspective view similar to FIG. 1 but showing a slightly different contact;

FIG. 5 is a perspective view of a blank from which the contact of FIG. 1 is completed; 7

FIG. 6 is a schematic view showing the tail of a contact being processed between the coining dies; and

FIG. 7 is a view similar to FIG. 6 showing the completed coining action.

Referring now in greater detail to the various figures of the drawing wherein similar reference characters refer to similar parts, a one-piece electrical contact embodying the present invention is generally shown at 10 in FIG. 1 and comprises a head section 12 and a tail section 14. The head section 12 basically comprises resilient fingers 16 and 18 which lie generally parallel to each other and which tightly grasp an inserted probe member of a male contact such as probe 20 of FIG. 2 of circular configuration or probe member 22 of FIG. 3 of rectangular configuration. Lugs 24 stamped from the interior surfaces of the contact fingers 16 and 18 assist in insuring good contact between the contact fingers and the probe. Curved lip 26 as the upper end of contact finger 16 aids the entry of the probe 20. The upper edge of contact 18 is beveled as at 28 to likewise facilitate the entry of the contact probe. Contact finger 18 merges at its lower end into U-shaped connecting arm 30 which in turn merges With contact finger 16 and tail section 14.

In the manufacture of contact 10, a stamping in an intermediate stage such as that shown in FIG. 5 is formed using well known progressive dies acting; upon a web of a known resilient good conducting metal such as spring grade tempered Phosphor bronze of thickness in the range of .020 inch to .026 inch in thickness as by way of example. As the stamping is produced and formed by the progressive dies, the lugs 24 are also formed in the contact fingers 16 and 18. At a desired stage, contact finger 1% is so bent as to lie generally parallel to the contact finger 16 and in so doing, the connecting arm 30 is formed. At about the same time, the corrugations of contact fingers 16 and 18 and the bevel 28 in contact finger 18 may be formed. The final step in making of the one-piece contact 10 is to convert the tail section 14 from that of a relatively slim rectangular cross-section to one having a thicker cross-see tion or a square cross-section. The foregoing sequence may be varied wherein, for example, the thickening of the contact tail occurs first or at some intermediate time and the other bending and forming steps occur in desired sequence before or after the thickening operation.

The pressure exerted by pressure members 34 and 36 with jaws 38 and mid-points 40 causes the metal of the contact tail 32 to flow thereby producing a cold working action. As the metal of tail 32 flows, the coining members 34 and 36 approach each other until the jaws 38 of the members 34 and 36 abut as shown in FIG. 7. With the abutment of the jaws, the metal of the heretofore rectangular tail 32 has been caused to flow in the retaining areas 44 extending between the jaws 38. Each retaining area 44 constitutes one half of a square, but other configurations are contemplated.

Hence, when the jaws 38 abut, the retaining areas 44 combine to form a square into which is confined the heretofore thin rectangular tail section 32. Thus, the rectangular tail section 32 has now become the square tail section 14. The V-shaped sharp edges 40 of the coining tool grab the heretofore rectangular tail 32 at the center of its thickness on the two short sides. In so doing the squared tail section 14 possesses two longitudinal grooves 46 which do not in any way interefere with the action of the automatic wire wrapping machine because the corners of the square tail 14 are sharp.

In this connection it should be noted that the reshaping of the contact tail under the process of the present invention produces a tail with corners much sharper than those produced in a cutting process. Thus, the leads from an outside circuit will be caused to dig more deeply into the contact tail when wrapped thereupon.

It has been found that a square tail with a dimension of 0.045 inch on a side to accommodate the automatic wrapping machine may be produced from a contact tail of spring grade tempered Phosphor bronze having initial dimensions of 0.022 by 0.093 inch and 0.026 by 0.078 inch. It is to be noted from FIG. 5 that slits 33 are provided above rectangular tail 32 to compensate for any slight upward expansion during the coining process.

An alternative method of thickening a contact tail is to utilize the direct vertical action of an overhead press upon the short side of the rectangular tail to achieve the thickening action. The contact would be tightly secured in a vice or other gripping device which would include an area for expansion of the contact tail under cold flow. Thus, there is one fixed jaw and one movable jaw, but the apparatus is otherwise generally similar to that shown in FIGS. 6 and 7. In this connection it should be noted that FIG. 6 may represent the initial coining operation and FIG. 7 represents the final operation. Thus, there may be used additional dies for intermediate operations to convert the technique of FIGS. 6 and 7 to a progressive die operation.

The use of progressive die techniques is desirable as metal which is made to flow too rapidly may contain induced stresses or warpage. This is avoided by making the metal flow in several steps under the action of the progressive dies.

It is also to be noted that the thickened or stiffened tail as shown in FIG. 7 will possess depressions 45 formed in the sides which have been shortened by virtue of the action of the coining dies. These depressions result from the inward flow of the metal.

It should be apparent that many varieties of contacts may be produced in view of the teachings of the present invention. The head section of the contact may assume different forms such as the one shown in FIG. 4 wherein the lugs 24 had been omitted and the contact finger 16 has a central longitudinal slit 46 formed as the contact head consists of two bends 48 and 50 uniting the contact fingers 16 and 18. Also the contact tail may be thickened or converted to other desired shapes.

It is thus seen that a contact of one-piece construction is provided which possesses contradictory properties. The head section is thin and resilient whereas the tail section is of a relatively thick cross-section and is relatively stiff.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed as the invention is:

1. The method of manufacturing a one-piece contact having the contradictory properties of a resilient head section of thin rectangular material and a stiff, sharply defined tail section of a substantially thicker rectangular cross-section than said head section, said method comprising providing a one-piece blank of uniform thin rectangular cross-section which is essentially completely thin and resilient throughout, said blank including a resilient head section of thin rectangular material and a resilient tail section of the same thin rectangular material, the head and tail section of said blank each having a short rectangular dimension and a long rectangular dimension; subjecting said thin resilient tail section including the short dimension thereof to the action of a pair of confining dies defining said sharply defined, substantially thicker rectangular cross-section with sharp corners, whereby to cold coin said blank tail section and to induce cold flow thereof to increase the short rectangular dimension of said blank tail section and decrease the long rectangular dimension thereof to produce a stiff tail section of a substantially thicker rectangular cross-section than said head section, said tail section being sufficiently stifi and work-hardened to withstand substantial wrapping pressures during the wrapping of the lead of an outside circuit thereabout and having sharp corners to enable said lead of an outside circuit to dig more deeply into said tail section during said wrapping thereof.

2. The invention of claim 1 wherein said confining dies define a square whereby to produce a stifi tail with a square cross-section.

References Cited in the file of this patent UNITED STATES PATENTS 1,674,318 Carr June 19, 1928 1,707,543 Stocking Apr. 2, 1929 2,294,802 Reich Sept. 1, 1942 2,377,974 Sherman June 12, 1945 2,597,153 La Garde et a1 May 20, 1952 2,601,462 Streader June 24, 1952 3,042,099 Neely July 3, 1962 

1. THE METHOD OF MANUFACTURING A ONE-PIECE CONTACT HAVING THE CONTRADICTORY PROPERTIES OF A RESILIENT HEAD SECTION OF THIN RECTANGULAR MATERIAL AND A STIFF, SHARPLY DEFINED TAIL SECTION OF A SUBSTANTIALLY THICKER RECTANGULAR CROSS-SECTION THAN SAID HEAD SECTION, SAID METHOD COMPRISING PROVIDING A ONE-PIECE BLANK OF UNIFORM THIN RECTANGULAR CROSS-SECTION WHICH IS ESSENTIALLY COMPLETELY THIN AND RESILIENT THROUGHOUT, SAID BLANK INCLUDING A RESILIENT HEAD SECTION OF THIN RECTANGULAR MATERIAL AND A RESILIENT TAIL SECTION OF SAID BLANK EACH HAVING A SHORT RECTANGULAR DIMENSION AND A LONG RECTANGULAR DIMENSION; SUBJECTING SAID THIN RESILIENT TAIL SECTION INCLUDING THE SHORT DIMENSION THEREOF TO THE ACTION OF A PAIR OF CONFINING DIES DEFINING SAID SHARPLY DEFINED, SUBSTANTIALLY THICKER RECTANGULAR CROSS-SECTION WITH SHARP CORNERS, WHEREBY TO COLD COIN SAID BLANK TAIL SECTION AND TO INDUCE COLD FLOW THEREOF 